Centrifugal pump



J. KIRGAN CENTRIFUGAL PUMP May 6, 1930.

Filed DeC. 20, 1928 Igvr/Ezvolef r n Kajal@ f v .Hm/ATTORNEY vPatented May 6, 1930 UNITED STATES PATENT oFFlcE JOHN KIRGAN, F EASTON, PENNSYLVANIA, ASSIGNOR T0 INGERSOLL-.RAND COH- PANY, 0F JERSEY CITY, JERSEY, A CORPORATION 0F NEW JERSEY CENTRIFUGAL PUE? Appucationv medneceniber 2 0, 192s. serial No. 327.3%.

The principal object of this invention is to increase the efficiency of a multiple stage centrifugal pump in which the suction pressure is extremely low inthe first stage. To-

ward this end the invention contemplates the interposition of a valve controlled bypass between the two stages of a hotwell pump to maintain a constant head on the lirst stage impeller of the pump. Thisl application contains subject matter kindred to that of my cQ-pending application bearing Serial No. 327,393, filed December 20, 1928, by\ me for an improvement in a cen- '20 trifugal pump and the general objects of this invention have been fully set forth in this copending application.

These objects have been accomplished byr means of the structure shown in the accompanying drawings in which: 4

The figure is a sectional view taken through a hotwell pump embodying the principles of this invention.

A pump is shown as being mounted on a 3o suitabl support 10 upon which there is a casing formed of an upper part 11 and a lower part 12. The lowerpart 12 is provided with a base 13. A drive shaft 14 extends between the upper and lower parts 11 and 12 and is suitably mounted so as to permit the same to rotate within the casing. The pump illustrated is of the two stage type, there being provided a first stage Wheel 16 and a second stage wheel 18, the second stage wheel being commonly known as the high pressure wheel. Both wheels are supported and driven by a single central shaft 14. .The irst stage wheel 16, is shown as being provided with relatively large inlets 22 in order that the velocity set up may be relatively low. Similarly, the outlets 23 from the first stage wheel, are relatively large and the diameter of the wheel is comparatively small, in order that the peripherial, relative and absolute velocities may be kept low in this stage. lThe pump as shown is designed to bring the discharge pressure up to at least atmospheric pressure. The second wheel or impeller 18, is provided with a comparatively small inlet 30 and a small discharge opening 31. This second impeller is designed to work with a slight pressure atits inlet. The casing 12 of the pump is provided with an inlet 40 located between/the two impellers 16 and 18. This inlet communicates with a passage 41 leading to the impeller inlets 22. The passage 41 is formed by Webs 43 cast integrally with the upper and lower parts 11 and 12 of the casing. These webs also serve as a partition to form the discharge passage leading to the second stage impeller 18.

The above mentioned parts are conventional in their design, having been patented to McIntyre. as cited above. The invention resides rather in the arrangement of parts now to be more fully described and claimed.

A cylinder is suitably mounted on the base 10 and one'end of the cylinder is provided with a reduced portion 63 providing a valve seat 64." The reduced portion of the cylinder 60 is closed at one end. Adjacent this end it is connected to the exhaust'side of the second stage wheel by means of a suitable connection 65. A piston 66 is slidablyl mounted in the cylinder. This vpiston has a reduced body portion 67 and a valve 68 is formed integrally with the reduced portion. The reduced portion 63 of the cylinder 60 provides a chamber 69- in which is disposed an extension 70 formed on the valve 68. The inlet side of the pump is connected directly to the cylinder at 73 by means cfa suitable connection 74 so that the pressure on the working side of the piston 66 will at all times equal the pressure in the condenser or in the outlet line leading therefrom.

The cylinder is closed at one end by a cap 8O having a central aperture 81 and a bushing 82 therein, through which aperture and bushing extends a valve stem 83 which terminates in a piston 84 forming one element of a dash pot assembly 85.

In actual operation when the first stage wheel is working under a full head, Huid is pumped directly from the outlets of the irst.

, the pump to the inlet to supply additional uid to the first stage wheel to prevent cavitation. When the first stage wheel has received suiicient fluid to again build up pressure on its exhaust side, thls pressure is transmitted through the line 61 to the chamber behind the piston 66 to force the piston forwardly and cose the valve 64. While the dashpot assem ly 85 is not essential to the invention, the same assures an even action of the piston in the cylinder and prevents sudden fluctuations in pressure in the hotwell Pump.

The invention 1s not necessarlly hmited to the exact arrangement of parts shown in the figure as modifications of the invention are contemplated. For example, the dashpot 85 may be replaced by any other suitable damping mechanism, such as a spring or the like and only in so far as the invention is particularly pointed out inthe claims is the same to be limited.

1. A multiple stage pumping system including a pair of impellers, each impeller operating to receive fluid from a fluid inlet and to discharge the same with increased head through a fluid outlet, a connection between the second stage outlet and the irst stage inlet, a valve in said connection, said valve being automatically opened upon a reduction in pressure in the flrst stage uid outletf to maintain a constant fluid head on the first stage impeller.

2. A multiple stage pumping stem including a irst stage impeller andya second stage impeller, each impeller operating to receive fluid from a fluid inlet and to discharge the same with increased head through a fluid outlet, a cylinder, a piston in said cylinder, a valve on said piston, there being a valve seat in said cylinder for said valve, a connection from the outlet side of the first stage impeller to said cylinder on one side of said piston, and a connection from the inlet side of the pump to the other side of said piston in the cylinder,and a connection from the outlet side of the second stage impeller to the cylinder on the opposite side of the Valve seat from said first mentioned connection.

3. A multiple stage pumping system in-` cluding first and second stage impeliers, each^ impeller operating to receive iuid from the fluid inlet and to discharge the same with increased head through fluid outlets, a connection between the second stage outlet and the irst stage inlet, afdiiferential valve controlling the connection and having its larger area constantly exposed to discharge pressure from the irst stage outlet and the smaller area of the valve being constantly exposed to discharge pressure from the second stage, thereby enabling the valve to be opened to by-pass fluid from the second stage outlet to the {i1-st stage inlet upon a reduction in pressure in the first stage outlet.

In testimony whereof I have signed this specification.

JOHN KIRGAN. 

